The present invention relates to plasma display panels (PDPs) and more particularly to a structure of discharge cells between barrier walls of alternating current discharge type PDPs with improved characteristics.
A manufacturing process of a conventional alternating current discharge type plasma display panel (PDP) 10 is shown in FIG. 1. First, two different activation layers are formed on glass substrates 11 and 12 respectively. Then the peripheries of substrates are sealed. A mixed gas consisting of helium (He), neon (Ne), and xenon (Xe) (or argon (Ar)) having a predetermined mixing volume ratio is stored in a discharge space therein. A front substrate 11 is defined as one that faces viewers. A plurality of parallel transparent electrodes 111, a plurality of bus electrodes 112, a dielectric layer 13, and a protective layer 14 are formed from the front substrate 11 inwardly. Correspondingly, from rear substrate 12 inwardly, a plurality of parallel data electrodes 121, a dielectric layer 124, a plurality of parallel spacer walls 122, and a uniform phosphor layer 123 are formed. When a voltage is applied on electrodes 111, 112, and 121, dielectric layers 113 and 124 will discharge to discharge cell 13 formed by adjacent barrier walls 122. As a result, a ray having a desired color is emitted from phosphor layer 123.
Conventionally, in PDP 10, a plurality of parallel transparent electrodes 111 are formed on an inner surface of front substrate 11 by sputtering and photolithography. (or printing). Then a plurality of bus electrodes 112 are formed on the transparent electrodes 111 by plating (or sputtering) and photolithography. The line impedance of the transparent electrodes 111 may be reduced by the provision of bus electrodes 112. In the following description, two adjacent transparent electrodes 111 (including bus electrodes 112) on the front substrate 11 are represented by an X electrode and a Y electrode respectively. A triple electrode is formed by the X electrode, Y electrode and corresponding data electrode 121 on the rear substrate 12. When a voltage is applied on the triple electrode, dielectric layers 113 and 124 will discharge to discharge cell 13 formed by adjacent spacer walls 122. Hence, UV rays are emitted from the mixed gas stored therein. And in turn, phosphor layer 123 in discharge cell 13 is excited by the UV rays. As an end, visible light is generated by the red, green and blue phosphor layers, resulting in appearance of an image.
As shown in FIGS. 1 and 2, a plurality of parallel barrier walls 122 are provided on back substrate 12. A plurality of parallel data electrodes 121 are provided on the underside of dielectric layer 124. Barrier walls 122 and data electrodes 121 alternate, with barrier walls 122 being positioned between data electrodes 121. A discharge cell 13 is formed between two adjacent barrier walls 122. A phosphor layer 123 is coated on discharge cell 13, opposite walls of barrier wall 122, and dielectric layer 124 respectively. However, several drawbacks have been found as detailed below
(a) The coating area of phosphor layer 123 is small: In view of back substrate 12, phosphor layer 123 is only allowed to be coated on discharge cell 13, opposite-walls of barrier wall 122, and dielectric layer 124 respectively. This may lower the emissivity of PDP 10.
(b) Discharge area is small: Referring to FIG. 3, there is shown a sectional view of adjacent discharge cells 13 with a suitable distance D formed therebetween in the conventional alternating current type PDP 10. Such distance D is provided for avoiding an undesired discharge. However, the provision of distance D may narrow the discharge cells 13 (i.e., opening too narrow), resulting in a lowering of emissivity. To the contrary, a small nondischarge cell may provide a large discharge space for obtaining an increased emissivity. However, this may also tend to cause undesired discharge which in turn has an adverse effect on the adjacent discharge cell.
(c) Subject to undesired discharge: Referring to FIG. 4, there is shown two adjacent discharge regions A and a sandwiched non-discharge region B in the conventional alternating current type PDP 10. It is seen that there is no barrier between two adjacent discharge regions A. Hence, it is subject to undesired discharge in non-discharge region B.
(d) Additional processing required: Referring to FIG. 5, there is shown two adjacent discharge regions A, a sandwiched non-discharge region B, and a hatched region C. The hatched region C is where additional processing on non-discharge region is performed for blocking light emitted from non-discharge region B, thereby obtaining a strong contrast of the image shown on PDP 10.
A number of proposals regarding the structure of the barrier wall have been submitted by PDP designers and manufacturers for solving the above drawbacks. For example, Pioneer Company (Japan) discloses a waffle-like barrier wall 622 as shown in FIG. 6. The phosphor layer is respectively coated on the top, bottom, left, right, and 20 underside of the discharge cell. Hence, the coating area of the phosphor layers is increased, resulting in an increase in emissivity. Also, the discharge cell is enclosed for eliminating undesired discharge in their non-discharge region. However, such enclosed discharge cell may increase difficulty of vacuum and gas filling. Another design is disclosed by Fujitsu Company (Japan) wherein barrier wall 722 has a meander rib structure as shown in FIG. 7. Such structure can increase the coating area to a maximum. However, this design suffers from several disadvantages. For example, phosphor layer printing is difficult in the process. As a result, colors tend to mix. Further, uniformity of phosphor layer printing is not obtainable. This in turn increases manufacturing cost and difficulty. Even worse, the yield is lowered. Moreover, a back substrate manufactured by such technique does not conform to the conventional front substrate. Hence, a specifically designed front substrate is required. As to drive technique, conventional drive techniques are not applicable if a complex drive technique such as ALIS is not adopted in conjunction therewith. In brief, despite achieving a maximum coating area the design proposed by Fujitsu Company is still disadvantageous due to problems associated with manufacturing process and drive technique.
It is thus an object of the present invention to provide, in an alternating current discharge type plasma display panel (PDP), a plurality of parallel barrier walls formed on the top surface of a back substrate of the PDP, the barrier walls being disposed corresponding to cross-points of X electrodes and Y electrodes on a front substrate of the PDP. The structure comprising the plurality of discharge cells between the adjacent barrier walls has a smaller width corresponding to the X and Y electrodes for forming a large first space, a plurality of non-discharge cells each between the adjacent discharge cells forming a small second space that serves as a gas channel between the adjacent discharge cells, and a junction having a predetermined shape between one discharge cell and the adjacent non-discharge cell, so that energy released from a gas is discharge in the discharge cells is concentrated within the discharge cells for increasing discharge efficiency, and emissivity, for avoiding undesired gas discharge, and for achieving a smooth vacuum and gas filling during the manufacturing process of PDP.
The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings.